1. Field
One or more embodiments relate to a lithium-transition metal complex compound having an nth order hierarchical structure, a method of preparing the same, and a lithium battery including an electrode comprising the lithium-transition metal complex compound having an nth order hierarchical structure. More particularly, one or more embodiments relate to a lithium-transition metal complex compound having an nth order hierarchical structure, which is derived from a natural material, a method of preparing the same, and a lithium battery including an electrode comprising the lithium-transition metal complex compound having an nth order hierarchical structure.
2. Description of the Related Art
Lithium ion batteries (LiBs) have been adopted as a power source of many portable devices due to their high energy density and easy design. Recently, there has been a trend to use LiBs as a power source of electric tools, electric bicycles, and electric vehicles, in addition to portable IT devices, and thus research has been actively conducted on an active material that has high power properties and can be charged rapidly. In general, in LiBs, graphite having a high theoretical capacity and a low charge and discharge potential has been used as an anode active material. However, the charge and discharge potential of graphite is close to 0 V, and thus, an LiB using graphite cannot be charged at a rapid rate. In addition, when an LiB using graphite is too rapidly charged, Li metal may be extracted from an anode of the LiB.
To overcome these problems, lithium titanium oxides (Li4Ti5O12 (LTO)) have been proposed as a new anode active material. LTOs show a stable and reversible charge/discharge curve at a potential of 1.5 V with respect to Li metal, and reach a theoretical capacity of 175 mAh/g. Moreover, the dimension of LTO is not changed by the intercalation/deintercalation of lithium ions, and thus LTO is referred to as a zero strain insertion material. In this regard, research has been actively conducted on LTOs that can be used as an active material that provides batteries with rapid charging and high power.
To increase the charge and discharge rates of LTO, the mass diffusion rate should be increased. For this, if the LTO is in nano-sized units, the specific surface area of the LTO increases, and thus a larger amount of a binder is needed for forming an electrode. In this case, the relative content of the LTO active material in an electrode is decreased, and thus the capacity of a battery including the electrode may be decreased.